Soft X-ray betatron radiation characterization for warm-dense matter studies at LCLS-MEC

Laser wakefield acceleration (LWFA) can produce high-energy ($>$100 MeV) electron beams with ultra-short durations ($<$100 fs)[1] in a compact, mm-scale plasma. Transverse motion of the electrons in the wakefield leads to the emission of synchrotron-like X-ray beams, called betatron radiation, with peak photon energies $>$10 keV and source sizes of a few microns [2]. These X-ray beams are presumed to retain the short-pulse characteristic of the electrons, resulting in high peak brightness and peak energy, making the source an excellent candidate for ultrafast temporally resolved pump-probe applications, especially for free-electron laser (FEL) and high-energy density (HED) experiments [3]. Presented here are some of first experimental measurements of betatron in the soft X-ray regime ($<$1 keV) using X-ray mirrors and a grating spectrometer to collect, transport, and focus betatron X-rays for pump-probe experiments at the LCLS Matter-in-Extreme Conditions (MEC) facility.\\[4pt] [1] O. Lundh et al., Nat. Phys. 2011\\[0pt] [2] S. Kneip et al., Nat. Phys. 2010\\[0pt] [3] F. Albert et al., PRL 2013